title: Activation of micro, delta or kappa opioid receptors by DAMGO, DPDPE, U-50488 or U-69593 respectively causes antinociception in the formalin test in the naked mole-rat (Heterocephalus glaber).
abstract: Data available on the role of the opioid systems of the naked mole-rat in nociception is scanty and unique compared to that of other rodents. In the current study, the effect of DAMGO, DPDPE and U-50488 and U-69593 on formalin-induced (20 microl, 10%) nociception were investigated. Nociceptive-like behaviors were quantified by scoring in blocks of 5 min the total amount of time (s) the animal spent scratching/biting the injected paw in the early (0-5 min) and in the late (25-60 min) phase of the test. In both the early and late phases, administration of 1 or 5 mg/kg of DAMGO or DPDPE caused a naloxone-attenuated decrease in the mean scratching/biting time. U-50488 and U-69593 at all the doses tested did not significantly change the mean scratching/biting time in the early phase. However, in the late phase U-50488 or U-69593 at the highest doses tested (1 or 5 mg/kg or 0.025 or 0.05 mg/kg, respectively) caused a statistically significant and naloxone-attenuated decrease in the mean scratching/biting time. The data showed that mu, delta or kappa-selective opioids causes antinociception in the formalin test in this rodent, adding novel information on the role of opioid systems of the animal on pain regulation.
authors.affiliation: Neurophysiology and Neuropharmacology Research Laboratory, Department of Veterinary Anatomy, University of Nairobi, P.O. Box 00100-30197, Nairobi, Kenya. towettp@yahoo.com
authors.forename: Philemon Kipkemoi
authors.initials: PK
authors.lastname: Towett
authors.forename: Titus Ikusya
authors.initials: TI
authors.lastname: Kanui
authors.forename: Geoffrey Moriaso Ole
authors.initials: GM
authors.lastname: Maloiy
authors.forename: Francis
authors.initials: F
authors.lastname: Juma
authors.forename: Jacob
authors.initials: J
authors.lastname: Olongida Ole Miaron
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D044482:Benzeneacetamides / Q000494:pharmacology*; D003627:Data Interpretation, Statistical; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology*; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology*; D005557:Formaldehyde; D007274:Injections, Intraperitoneal; D008297:Male; D019577:Mole Rats; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010146:Pain / Q000139:chemically induced / Q000517:prevention & control*; D010147:Pain Measurement / Q000187:drug effects*; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017465:Receptors, Opioid, delta / Q000819:agonists*; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D017450:Receptors, Opioid, mu / Q000819:agonists*
chemical_list: D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D044482:Benzeneacetamides; D009292:Narcotic Antagonists; D011759:Pyrrolidines; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D005557:Formaldehyde; D009270:Naloxone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D020881:Enkephalin, D-Penicillamine (2,5)-; C045444:U 69593